As a blood bag in which blood is put, blood bags made of a plasticized vinyl chloride resin have widely been used to date. The blood bag is used with a label describing about information of blood being attached thereon.
After the attached label is subjected to an autoclave treatment or a steam sterilization at 120° C. for about 30 minutes, there is an instance where plasticizers contained in a plasticized vinyl chloride resin move into an adhesive layer to lower the adhesive property of the label, and lifting or peeling of the label takes place. When the label is peeled off from the blood bag, information about the blood is lost, causing a serious problem. Further, even in this case, if the label is merely peeled off, the blood bag that the label was peeled off may be scrapped, but in the case where a plurality of labels are peeled off without someone's knowledge for some reason, and the labels are wrongly attached to one of the other blood bags again, a blood bag with wrong blood information is used, resulting in a further fatal problem.
Moreover, as a label for a blood bag, there is used a label on which a trade name, volume, ingredient representation, and manufacture etc. are printed. In this field, a bar-code management system is established, the label that bar-code are printed is required. As a label for a blood bag, conventionally a label of paper as a substrate has been mainly used. However, when such label is in application to a blood bag, there have been problems that in treatment by a centrifugal separator to separate a normal blood cell component, a blood plasma component and the other component, due to lack of strength of the label substrate, the label cannot endure a centrifugal force and is broken, cracked, or through friction of the printed surface against the wall surface or the blood bag surface, information such as bar-code becomes too unclear to read by a bar-code reader. Therefore, there has increasingly desired a plastic film substrate being less influenced by moisture than a paper substrate, and resistant to rubbing and strong/tough. However, although a plastic film substrate has the superiority described above, it has defect that lifting or peeling occurs more easily than a paper substrate in an autoclave treatment or a steam sterilization treatment and a centrifugal separation treatment. Further, when a heat sealing label is based on a plastic film substrate of liner-less roll type, it has a defect that blocking occurs more easily than a paper substrate.
To solve these problems, there is proposed a label for a blood bag based on a substrate film which is a microporous plastic film with a matrix structure surrounding pores connecting each other so that gas can flow in said blood bag and flow out through a region labeled (see Japanese Patent No. 3404573). Lifting and peeling in an autoclave treatment can be suppressed, however, there has been a problem that it is difficult to obtain the label with excellent blocking resistance.